QueryPerformanceFrequency,RDTSC,CPU频率

//warning C4035: 'RDTSC' : no return value

#pragma warning(disable:4035)

 

#include <Windows.h>

 

//RDTSC-Read Time-Stamp Counter

//自开机以来CPU经历的时钟周期数

unsigned __int64 RDTSC()

{

    __asm _emit 0x0F;

    __asm _emit 0x31;

}

 

//CPU的频率

double CpuFrequency()

{

    //On a multiprocessor machine, it should not matter which processor is called.

    //However, you can get different results on different processors due to bugs in

    //the BIOS or the HAL. To specify processor affinity for a thread, use the SetThreadAffinityMask function.

    HANDLE hThread=GetCurrentThread();

    SetThreadAffinityMask(hThread,0x1);  

   

    //主板上高精度定时器的晶振频率

    //这个定时器应该就是一片8253或者8254

    //在intel ich7中集成了8254

    LARGE_INTEGER lFrequency;

    QueryPerformanceFrequency(&lFrequency);

    //printf("高精度定时器的晶振频率：%1.0fHz.\n",(double)lFrequency.QuadPart);

 

    //这个定时器每经过一个时钟周期，其计数器会+1

    LARGE_INTEGER lPerformanceCount_Start;

    QueryPerformanceCounter(&lPerformanceCount_Start);

 

    //RDTSC指令:获取CPU经历的时钟周期数

    __int64 _i64StartCpuCounter=RDTSC();

 

    //延时长一点,误差会小一点

    //int nTemp=100000;

    //while (--nTemp);

    Sleep(200); 
 

    LARGE_INTEGER lPerformanceCount_End;

    QueryPerformanceCounter(&lPerformanceCount_End);

 

    __int64 _i64EndCpuCounter=RDTSC();

 

    //f=1/T => f=计数次数/(计数次数*T)

    //这里的“计数次数*T”就是时间差

    double fTime=((double)lPerformanceCount_End.QuadPart-(double)lPerformanceCount_Start.QuadPart)

        /(double)lFrequency.QuadPart;

 

    return (_i64EndCpuCounter-_i64StartCpuCounter)/fTime;

}

 

int main(int argc, char* argv[])

{

    printf("CPU频率为:%1.6fMHz.\n",CpuFrequency()/1000000.0);

    return 0;

}